Appendix

Slit-Skin Smears (or ‘Skin Scrapings’)

Slit-skin smears, also known as ‘skin scrapings’, are samples of dermal fluid obtained from several sites, smeared individually onto a glass microscope slide, and stained with the Fite stain, as described in the text. Examined microscopically under oil immersion (1000×) by a trained technician, the number of acid fast bacilli may be enumerated semi-quantitatively according to a six-point scale known as the Bacteriologic Index (BI) (35) as follows:

Representative oil-immersion fields for these different BI’s are shown in Figure A1.

Reliable, reproducible quantitation of the BI in slit skin smears is difficult and is performed optimally only by technicians experienced in obtaining, staining, and examining the smears